Natural deep eutectic solvents: A paradigm of stability and permeability in the design of new ingredients

Abstract

Ascorbic Acid (AA) is a crucial component in the food industry, serving as both a quality and safety criterion. It is used to fortify foods due to its significant role in human health, acting as an antioxidant. Its benefits extend to both product quality and consumer health in the food and cosmetic industry. Due to their physicochemical properties, Natural Deep Eutectic Solvents (NADES) have the potential to be used for the extraction and stabilization of bioactive compounds. The objective of this study is to characterize various NADES, simulate the solubility of AA, evaluate the antioxidant and protective capacity of NADES, and investigate the permeability of this vitamin through the skin and gastrointestinal membrane. Antioxidant capacity was measured using three methods: TEAC, DPPH, and ORAC. The solubility of AA in NADES systems was simulated using the COSMOTherm software. The degradation of AA was monitored by HPLC/UV–Vis for 30 days at two different storage temperatures. Additionally, the membrane solubility was measured using the PAMPA method in both skin and gastrointestinal. The results indicate that organic acid-based NADES are more polar than sugar and polyalcohol-based NADES. The solubility prediction shows that reduced ln(γ) in Choline chloride-based NADES results in low AA solubility, which positively correlates with higher pH values. AA degradation increased at lower pH, and its half-life time was longer at 4 °C, being the best choline chloride (ChChl):xylose. Moreover, betaine:malic acid, ChChl:tartaric acid, and ChChl:lactic acid gave worse stabilizing results than control. According to the PAMPA study, AA in lactic acid:glucose had the highest Pe (permeability coefficient) for both gastrointestinal (Log Pe: −4.99) and skin (Log Pe: −4.78). Malic acid:glucose, on the other hand, had the lowest LogPe value (−6.9). In this study, some NADES can play a protective role in the preservation of ascorbic acid. This statement could be extended to other bioactive compounds found in NADES extracts that may be impacted by oxidative processes. Moreover, not all NADES stabilized equally AA. These findings could be applied to the formulation of ascorbic acid-containing drugs, cosmetics, and food products.